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Re: 11th specimen of Archaeopteryx
On 10/27/2011 10:02 AM, Habib, Michael wrote:
On Oct 27, 2011, at 4:30 AM, Don Ohmes wrote:
I am agnostic on the limits on upstroke amplitude in basal birds due to
limited data and skills -- I am just pointing out that if they were
severely limited in the manner that I have read is ascribed to Arch.,
then a path to powered flight that did not initially exploit gravity as
the primary energy source rather than muscle power is not clear -- at
least to me.
One possibility would be that flapping strokes evolved from a precursor
behavior in a more terrestrial realm. In other words, the proto-flyers might
not have been flying.
Well, in general, yes -- it is just that a plausible specific behavior
or lifestyle that incrementally takes a skeleton from limited upstroke
(as ascribed to Arch. by some) to powered flight w/out going through a
gravity-powered phase has not been advanced.
I suppose Arch. or some relative could have been fanning his/her eggs to
cool them down, or drumming grouse-style -- and then bim bam boom!, we
have a tweety-bird in the house.
But that is the best I can do, and those seem comparatively weak to me.
One weak point is that the above mentioned non-flight-related
pre-powered-flight behaviors don't provide a clear path to evolution of
brain/nervous system control mechanisms.
Or, to re-state -- if control surfaces and asymmetrical primaries appear
prior to a full up-stroke, the more parsimonious path to flight is NOT
'ground-up' or 'active' or whatever the latest term is...